It is of great interest to recover valuable components that can be recycled by treatment and cleaning of drilling mud, such as the original drilling mud, including particular components added to this in order to reach desired characteristics, said components also being of particulate form.
In addition, environmental considerations and labor conditions have recently gained increasing interest. It is known that the oil industry is responsible for considerable releases of environmentally hazardous materials, and that workers, e.g. on the platforms, have been exposed to considerable amounts of health-hazardous substances.
Norwegian Patent no. 172568 describes a method and device for treatment of returned drilling mud during oil and gas drilling. Included is a degassing step, a vibrating screen shaker, and one or more steps of separating coarse to fine cuttings from drilling mud, as well as a transport system for transporting the cuttings. One of the features characterizing this method is the use of a so called screw classifier as a first separating step. A disadvantage of this system and other similar systems using conventional vibrating screen shakers is that the cuttings, e.g. if the crown bit penetrates particularly difficult formations, clogs the screen shaker. In this case the screen must be manually scraped and de-clogged. Of this reason, the screen shaker system must be partly open, in order to give access for the workers with their tools. In this case, the workers are also exposed to chemicals and gasses present in the drilling mud and cuttings.
In systems known today, the separated cuttings contain too much drilling mud, resulting in a relatively large loss of active drilling mud, leading to considerable economic loss.